The aging of the component units and the different damage mechanisms

In the scope of the nuclear power plants lifetime evaluation, the different damage mechanisms of the plant units or materials, are investigated. The study includes the materials aging under the effect of temperature or neutrons, and mechanical stresses. The erosion-corrosion or corrosion problems are not considered. The work leads to the following conclusions: the manager, warned by the oldest unit accidents, is induced to carry out the reexamination of some of the plant units, to avoid exploitation problems; the difficulties are related to a fast aging or the need to take into account in the materials fabrication, loads or stresses which are not well known; inspection renewal is effectuated under a lifetime extension project; and that the decenial checkout, which allows the observation of the most sensitive zones and the required changements, are essential